Cell biology is the study of the units that compose all living organisms. This field investigates the structure, function, and behavior of cells, from simple bacteria to the complex cells that make up the human body. Understanding how cells work is foundational to all biological sciences. By examining cells in healthy and diseased states, scientists develop new vaccines and medicines, informing fields from regenerative medicine to agriculture.
The First Glimpses into the Cellular World
The 17th century marked the beginning of our journey into the microscopic world. In 1665, English scientist Robert Hooke used a microscope to examine a thin slice of cork. He observed a porous structure that reminded him of the small rooms in a monastery, leading him to coin the term “cell” from the Latin word cellara. His observations in Micrographia were the first to describe these basic biological structures.
Around the same time, Dutch draper Antonie van Leeuwenhoek was making powerful single-lens microscopes. His skill in grinding lenses achieved magnifications greater than 200 times, revealing a previously unseen world of living organisms. In 1674, he was the first to observe single-celled organisms, which he called “animalcules,” in pond water and scrapings from his teeth. These observations of bacteria and protozoa laid the groundwork for bacteriology and protozoology.
Establishing the Foundations of Cell Theory
The discovery of cells in the 17th century set the stage for the 19th-century formulation of Cell Theory, which was a collaborative effort. The theory began with German scientists Matthias Schleiden, a botanist, and Theodor Schwann, a zoologist. In 1838, after studying plant tissues, Schleiden concluded that all plants were composed of cells.
Inspired by Schleiden’s work, Schwann investigated animal tissues and, in 1839, proposed that animals are also made of cells. This led to the first two principles of cell theory: all living things are composed of one or more cells, and the cell is the basic unit of life. They believed that cells could form spontaneously, an idea later corrected by German physician Rudolf Virchow.
In 1858, Virchow completed the core tenets of modern cell theory by stating, “Omnis cellula e cellula,” which translates to “all cells arise from pre-existing cells.” This principle refuted the idea of spontaneous generation and established that cells are self-reproducing entities. The work of these three scientists provided a foundational framework for biology.
Unveiling the Inner Workings of the Cell
After cell theory was established, focus shifted to the machinery within the cell. In 1898, Italian physician Camillo Golgi developed a staining technique using silver nitrate to make cellular structures visible. While studying nerve cells, he identified an internal structure now known as the Golgi apparatus. This organelle functions as a cellular “post office,” modifying, sorting, and packaging proteins and lipids for delivery.
Romanian-American cell biologist George Palade used the electron microscope in the 1950s to make further discoveries. He identified small particles, often attached to the endoplasmic reticulum, which he called “ribosomes.” Palade demonstrated that ribosomes are the sites of protein synthesis, effectively the cell’s “protein factories.” His work tracing the path of proteins provided a map of the secretory pathway.
Belgian cytologist Christian de Duve identified another organelle through his work on enzymes in the 1950s. He noticed that digestive enzymes were contained within a membrane-bound sac, preventing them from damaging the rest of the cell. He named this organelle the “lysosome,” which acts as the cell’s recycling center by breaking down waste materials. This discovery revealed the cell to be a highly organized system.
Revolutionary Theories and Modern Pioneers
American biologist Lynn Margulis advanced cell biology with her endosymbiotic theory. In the late 1960s, she proposed that organelles like mitochondria and chloroplasts were once free-living bacteria. According to her theory, these bacteria were engulfed by larger host cells and developed a symbiotic relationship, evolving into the organelles we know today. Though initially met with skepticism, this idea is now supported by evidence that these organelles have their own DNA resembling bacterial DNA.
Japanese cell biologist Yoshinori Ohsumi received the Nobel Prize in 2016 for his discoveries of the mechanisms for autophagy. Autophagy, or “self-eating,” is the process where cells degrade and recycle their own components. Ohsumi used baker’s yeast to identify the genes involved in this process, which helps cells survive starvation and eliminate damaged proteins. This cellular housekeeping is important for preventing diseases like cancer and neurodegenerative disorders.
Japanese stem cell researcher Shinya Yamanaka was awarded the Nobel Prize in 2012 for his work on induced pluripotent stem cells (iPSCs). In 2006, he discovered that mature adult cells could be reprogrammed back into a pluripotent state by introducing just four specific genes. These iPSCs behave like embryonic stem cells and can develop into any type of cell in the body. This technology allows for the creation of patient-specific cells to study and treat diseases.